(1) Field of the Invention
The present invention relates to gear shift control apparatus and method for an automatic transmission in which a command hydraulic pressure supplied to an engagement side frictional engagement element is temporarily reduced at an inertia phase finish immediately prior region developed in a midway through a progress of a gear shift.
(2) Description of Related Art
A Japanese Patent Application First Publication No. Heisei 10-47464 published on Feb. 20, 1998 (which corresponds to a U.S. Pat. No. 5,857,935 issued on Jan. 12, 1999) exemplifies a previously proposed up-shift control apparatus for the automatic transmission in which a hydraulic pressure supplied to a clutch engaged along with a gear shift is stepwise reduced to reduce a shock in a gear shift finish region when a speed ratio has reached to the speed ratio representing an inertia phase finish immediately prior region.
It should, herein, be noted that the term of “inertia phase” is one of phases developed in a midway through a progress of a gear shift and is a phase in which an input revolution speed of the automatic transmission is varied with a main cause of a variation of an inertia force (inertia) of a drive-train in which an automatic transmission is equipped. A control of a command hydraulic pressure for an engagement side frictional engagement element in which the command hydraulic pressure is temporarily reduced is carried out at the region immediately before the finish. Hence, this control is, hereinafter, called a finish pressure control.